How to spray liquid chlorine on black algae

[Klutz14159]

My plaster pool is getting more and more hairline cracks and they are all turning black. Stainless steel brushing gets some of it out, but with pretty limited effect. For the larger patches, I tried rubbing trichlor pucks, but they wear down quickly and the holder doesn't is tough to adjust.

I read some posts about using a liquid chlorine pump spray for spot treatment after scrubbing. Given the size of my pool and some of the cracks being in the deep end, I was wondering how you spray the LC into those spots. Can you submerge the whole tank and sprayer mechanism and stand inside the pool while spraying? Or am I going to end up with chlorine skin burns that way?

Feel free to post Amazon links to sprayers that would do the job.

Also, can you handle trichlor pucks underwater by hand? I have gloves, but obviously gloves only go halfway up the arm, and my face is going to be within 2 feet of wherever I'm rubbing those pucks.

 

[PoolGate]

I have never heard of spot treating algae. Can you post a full set of test results? Sounds simply like your chlorine level is not high enough to keep your pool clean and sanitary.

 

[Klutz14159]

FC 5 in evening, topped up to 8 at night, OCLT <0.5 consistently
pH 7.5
CC 0
CYA 40
CH 250
TA 90
water temp 84F with solar cover

This is a really old IG pool and the plaster is probably at least 15 years old and chunks are coming off, the black algae is in all the numerous cracks and pitted areas. I had let FC drop down to 0-1 over the winter occasionally, but have kept FC > 3 since end of March, and >5 since start of June when school let out and we have kids and teachers in pool 4hrs a day.

 

[PoolGate]

FC 5 in evening, topped up to 8 at night, OCLT <0.5 consistently
pH 7.5
CC 0
CYA 40
CH 250
TA 90
water temp 84F with solar cover

This is a really old IG pool and the plaster is probably at least 15 years old and chunks are coming off, the black algae is in all the numerous cracks and pitted areas. I had let FC drop down to 0-1 over the winter occasionally, but have kept FC > 3 since end of March, and >5 since start of June when school let out and we have kids and teachers in pool 4hrs a day.

Do you use "Pool Math"? If so, can you share your results with the forum? With proper chlorine levels your pool should not develop any algae. Are you sure this is algae? Can you post a pic? Try raising your FC to 10 for a couple weeks.

Chlorine / CYA Chart

 

[Klutz14159]

No, I use PoolMath mostly. Phone apps are too small for my presbyopic eyes. Will try to take a picture one of these days. It's always tough to get good light, and when there's the right light, I'm usually too busy scrubbing the pool